Field of the Invention
The present invention relates to a gas sensor which includes a tubular metallic shell having an axial hole, and a plate-like gas detection element inserted into the axial hole and held to the metallic shell and which detects a particular gas component contained in gas to be measured, and to a gas detection element for use in the gas sensor.
Description of Related Art
Conventionally, there is a gas sensor disposed in, for example, an exhaust pipe of an internal combustion engine and adapted to detect a particular gas component contained in gas to be measured, such as an oxygen sensor for detecting the oxygen concentration of exhaust gas. A known gas sensor of this type includes a tubular metallic shell having an axial hole, a single or a plurality of holding members disposed in the axial hole, and a plate-like gas detection element which is held to the metallic shell through the holding member(s).
The gas detection element has a detecting section provided at an element forward-end portion located forward of the holding members, and adapted to detect a particular gas component contained in gas to be measured. The gas detection element also has electrode pads provided on an element rear-end portion located rearward of the holding members; furthermore, in some cases, the gas detection element has through hole conductors provided in the element rear-end portion and electrically communicating with the electrode pads, respectively. Terminal members come into contact with the respective electrode pads on the element rear-end portion. Also, a certain detection element is configured such that the element rear-end portion is exposed to a reference gas space (for example, a space filled with reference gas, such as the air), and configured to have a reference gas introduction passage formed therein and extending from an opening formed at the element rear-end portion to the detecting section for introducing reference gas to the detecting section from the reference gas space. For example, Patent Document 1 discloses a gas sensor having such a gas detection element (refer to FIGS. 1 to 3 and description associated therewith in Patent Document 1).